This invention relates in general to the protection of wood frame buildings against seismic and wind forces and, more particularly, to a system which can be applied to existing wood frame building to provide such protection.
Modern building constructed over the last several years in areas prone to seismic activity or high winds are provided with protection against those forces. Sturdy foundations and a variety of systems for tieing the building together and to the foundation are generally provided. In other cases, particularly with large buildings, various "floating" supports are provided, allowing the building to move or sway in response to seismic forces without damage.
Older buildings, mobile homes and the like are generally not well secured to their foundations and are prone to moving off their foundations during earthquakes or high winds such as tornadoes or hurricanes. Retrofiring these existing buildings to the standards for new construction is generally prohibitively expensive.
Even where older buildings were originally well fastened to their foundations, with time those fastening arrangements have often deteriorated. Building foundation mud sill plates on peripheral foundations often have studs embedded in the foundation extending through the sill plates with washers and nuts holding the sill plates to the foundation. Older building were often constructed with large aggregate and sandy cement concrete, what is now called rubble concrete. With time, the concrete weakens and crumbles, no longer holding bolts securely. The addition of more fasteners between foundation and building is generally ineffective where the foundation has deteriorated. The width of typical foundations is such that there is often only two inches of concrete on each side of a bolt. Also, many building foundation mud sill plates are not secured in any manner tho their foundations. Thus, in a earthquake the bolt may crack or split the foundation, allowing the structure to move off of the foundation, often causing total destruction. Further, even if the foundation is still sturdy, the sill plates may have deteriorated due to termites, dry rot or the like, increasing the chance of earthquake or wind damage.
A variety of bracing systems have been developed to try to tie buildings to foundations to resist seismic and wind forces. Typically, Biggane in U.S. Pat. No. 4,065,218 provides a reinforcement in which a channel iron is connected through articulated ends to a structure and to an object being supported, to provide support and flexibility. Ikue et al in U.S. Pat. No. 4,441,289 describes a compression brace system for diagonally reinforcing a pillar beam building. Murray in U.S. Pat. No. 4,615,157 discloses a system for damping oscillations in floor joists. Johnson in U.S. Pat. No. 5,072,570 discloses a brace bolted to the side of a concrete foundation and floor beams to tie them together. While effective in some cases, these arrangements are often difficult to apply to existing structures, are expensive and may require undeteriorated foundation and adjacent wooden structures and may not improve resistance to severe seismic forces and high wind forces.
Thus, there is a continuing need for improved systems for modifying existing wood frame structures to resist seismic and wind forces, which are inexpensive, effective, and can be easily applied to existing structures, even those which have deteriorating peripheral foundations and/or deteriorating wood in sill plates and similar components.